Needs for techniques for selectively separating cells from a patient's blood are increasing along with the development of cancer therapy or transfusion of cellular blood components, and particularly in light of the recent development of cellular medicine and regenerative medicine. Removal of granulocytes from blood is particularly important in order to suppress inflammation or graft-versus-host-disease (GVDH) after implantation. For example, the following techniques for separating granulocytes from blood have been disclosed in the past: specific gravity and density gradient centrifugation involving the use of a Ficoll or Percoll solution to separate cells based on differences in specific gravity of the cells; and a method involving the use of a material that is assumed to selectively adhere to granulocytes, such as polyester fibers, nylon fibers, or cotton (e.g., JP Patent Publication (kokai) Nos. 54-46812 A (1979) and 57-11920 A (1982)).
A specific gravity and density gradient centrifugation technique, however, still has many drawbacks. Examples include safety issues such as in regards to cytotoxicity of a density gradient solution; operability issues, such as the time required for operations such as centrifugation or washing, along with contamination resulting from operations in an open system; and low separation efficiency arising from contamination with lymphocytes. In contrast, a method for selectively adsorbing granulocytes is superior to methods involving specific gravity and density gradient centrifugation in terms of safety and operability since such technique can be carried out in a closed system. Also, modifications of contact areas, materials, configurations, and other conditions have been attempted in order to further improve separation efficiency.
JP Patent Publication (kokoku) No. 58-54126 B (1983) discloses a technique for increasing the surface area of a granulocyte adsorbent. However, this document describes that the adsorbent also adsorbs lymphocytes in addition to granulocytes. That is, increase in contact areas does not lead to the expression of granulocyte selectivity. JP Patent Publication (kokai) No. 2-193069 A (1990) discloses a method for selectively adsorbing granulocytes using granulocyte-adsorbing carriers that have higher affinity for granulocytes than for lymphocytes and can be used for determining changes in the pathological conditions of a cancer patient or for cancer treatment.
Such carriers comprise substances each having a contact angle with water of 55 to 95 degrees, and materials having high affinity for granulocytes, such as polystyrene, cellulose acetate, 6-nylon, and polyethylene terephthalate, are provided as examples. Also, a similar report has been made concerning the contact angle and the adhesion rate of neutrophils, which are major constituents of granulocytes (the 19th Biomedical Polymers Symposium abstracts, pp. 51 to 52, the Society of Polymer Sciences, Japan, Jun. 11, 1990). In such report, neutrophils are reported to have higher affinity for a material with which the contact angle of an adhesion substrate with water is approximately 70 degrees, and the influences of materials are reported to be significant in the expression of granulocyte selectivity.
JP Patent Publication (kokai) No. 5-168706 A (1993) discloses that adhesion of granulocytes is not associated with the contact angle of a given material and is defined by the surface roughness of the contact surface. Thus, it has been demonstrated that mere increase of contact area is not sufficient in order to express granulocyte selectivity. Factors such as the surface roughness of the adhesive substrate and hydrophilic or hydrophobic properties (the contact angle) are associated with the selectivity. With the use of a material with a modified contact angle or surface roughness, granulocyte selectivity is not always satisfactory. Accordingly, development of a granulocyte-separating material, a granulocyte-adsorbing apparatus, and a method with improved selectivity for granulocytes has been awaited.
Existing commercially available granulocyte-adsorbing columns or leukocyte-adsorbing columns have drawbacks in terms of body fluid compatibility; that is, platelet adhesion. Large quantities of platelets adhere to areas in the vicinity of column inlets, resulting in elevated blood pressure or lowered blood platelet concentration.
Patent Document 1: JP Patent Publication (kokai) No. 54-46812 A (1979)
Patent Document 2: JP Patent Publication (kokai) No. 57-11920 A (1982)
Patent Document 3: JP Patent Publication (kokoku) No. 58-54126 B (1983)
Patent Document 4: JP Patent Publication (kokai) No. 2-193069 A (1990)
Patent Document 5: JP Patent Publication (kokai) No. 5-168706 A (1993)
Non-Patent Document 1: The 19th Biomedical Polymers Symposium abstracts, pp. 51 to 52, the Society of Polymer Sciences, Japan, Jun. 11, 1990